Processing copper base alloys

ABSTRACT

Copper base alloys are processed to obtain improved stress corrosion resistance coupled with high strength and favorable strength to bend ductility characteristics. The copper base alloys contain from 1 to 5% tin, 1 to 4.5% silicon with a minimum tin plus silicon of 3.5%.

United States Patent [191 Shapiro et al.

[ 1 Dec. 2, 1975 PROCESSING COPPER BASE ALLOYS [75] Inventors: Stanley Shapiro, New Haven;

Ronald N. Caron, Branford, both of Conn.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Oct. 4, 1974 [2]] Appl. No.: 512,259

[52] U.S. Cl. 148/115 A; 148/127 [51] Int. Cl. C22F l/04 [58] Field of Search 75/154, 160; 148/115 A,

[56] References Cited UNITED STATES PATENTS 1,956,251 4/1934 Price 75/154 2,035,414 3/1936 Wilkins r 75/154 2,035,415 3/1936 Wilkins i 75/160 2,052,523 8/1936 Wilkins 75/154 2,062,448 12/1936 Deitz, Jr. et al. 75/154 2,257,437 9/1941 Weiser 75/154 Primary ExaminerW. Stallard Attorney, Agent, or Firm-Robert H. Bachman; David A. Jackson [57] ABSTRACT 10 Claims, No Drawings PROCESSING COPPER BASE ALLOYS BACKGROUND OF THE INVENTION It is highly desirable to prepare copper base alloys having high mechanical strength, excellent stress corro--. sion resistance and general corrosion resistance especially in severe ammoniacal environments. It is also desirable to prepare a material of the foregoing type inexpensively and expeditiously on a commercial scale.

The preparation of a material of this type would satisfy the stringent requirements imposed by modern applications for electrical contact springs, for example, in which spring temper mechanical properties are required coupled with adequate bend formability and with stress corrosion resistance in severe ammoniacal environments which are generated during decomposition of organic electrical insulation materials.

Accordingly, it is a principal object of the present invention to provide a convenient and inexpensive process for preparing wrought copper base alloys having improved mechanical properties.

It is a particular object of the present invention to provide a process aforesaid which obtains wrought copper base alloys having excellent stress corrosion resistance in severe ammoniacal environments coupled with high strength and favorable strength to bend ductility characteristics.

Further objects and advantages of the present invention will appear hereinafter.

SUMMARY OF THE INVENTION In accordance with the process of the present invention it has been found that the foregoing objects and advantages may be readily obtained. The process of the present invention comprises: providing a copper base alloy containing from 1.0 to 4.5% silicon, 1.0 to 5.0% tin, with the minimum silicon plus tin content being 3.5%, balance essentially copper; hot rolling said alloy at a starting temperature in excess of 650C within 50C of the solidus temperature of the alloy, and with a finishing temperature in excess of 400C; cold rolling the alloy at a temperature below 200C; and annealing said alloy at a temperature of from 250C to 850C for from seconds to 24 hours. Naturally, several processing variations are contemplated within the scope of the present invention in order to obtain particularly preferred properties.

It has been found that the foregoing process inexpensively and conveniently obtained copper base alloys having the highly desirable properties referred to hereinabove.

DETAILED DESCRIPTION As indicated hereinabove, the copper base alloys processed in accordance with the present invention contain from 1.0 to 4.5% silicon and from 1.0 to 5.0% tin. The total silicon plus tin content should be a minimum of 3.5% in order to obtain adequate stress corrosion resistance and other desirable mechanical properties.

In accordance with the present invention it is highly preferred that the copper base alloys processed herein contain certain additives in order to provide preferred properties. The first additive which is preferably included in the foregoing copper base alloys is from 0.01 to 2.0% iron, from 0.01 to 2.0% cobalt and mixtures thereof, with a maximum total iron plus cobalt content being 3.0%. The second additive which is preferably included in the foregoing copper base alloys is selected from the following group and mixtures thereof: Nickel from 0.01 to 5.0%; manganese from 0.01 to 5.0%; titanium from 0.01 to 5.0%; zirconium from 0.01 to 5.0%; hafnium from 0.01 to 5.0%; chromium from 0.01 to 2.0%; beryllium from 0.01 to 3.0%; vanadium from 0.01 to 5.0%; andmagnesium from 0.01 to 2.0%. The total content of said first additives plus said second additives should be less than 10.0%.

Naturally, the first additive may be present in the alloy independently of the second additive, and the second additive may be present in the alloy independently of the first additive, so that the alloy may contain the first additive without the second additive, or the second additive without the first additive, or preferably both may be present together. If, therefore, the second additive is present in the alloy and the first additive is not present in the alloy, the total content of the second additive should be less than 10%.

In accordance with the process of the present invention, the silicon and tin components provide maximum solid solution strengthening and work hardening, with the silicon content being crucial for desired stress corrosion resistance. The first and second additives referred to hereinabove are preferred to obtain optimum physical properties. These materials generally form dispersed or precipitated second phases. The morphology of these phases is controlled during processing to provide dispersion strengthening and grain refinement and/or precipitation hardening especially during an aging treatment.

In addition to the foregoing, it is preferred to utilize a third additive selected from the following group and mixtures thereof, from 0.01 to 3.0% each of the following materials and mixtures thereof: Arsenic, antimony, aluminum and zinc. The foregoing third additives should be present in a maximum total of less than 5.0%. The aluminum addition is particularly desirable in combination with the nickel or manganese component. Naturally, the third additive may be present in the alloy independently of the first or second additives, or in combination with either the first or second additives, or preferably in combination with both the first and second additives.

' The alloys processed in accordance with the present invention may be cast by any suitable method. In order to provide a more homogeneous cast structure and better bar quality, direct chill or continuous casting procedures are preferred.

After casting the alloy is preferably heated at temperatures between 600C and the solidus temperature of the particular alloy for at least 15 minutes. The alloy is then hot rolled from a starting temperature in excess of 650C up to within 50C of the: solidus temperature of the alloy. The hot rolling finishing temperature should be in excess of 400C. The actual solidus temperature of the particular alloy will naturally depend on the silicon and tin contents and on the amount and nature of any additives. The hot rolling reduction is not critical and will depend upon final gage requirements.

After hot rolling it is preferred to quench the alloy if the alloy composition contains any of the first, second or third additives in order to maximize the amount of said additives which remain in solution. This is particularly preferred with respect to the second additives since they are substantially precipitated out of solution by subsequent processing in order to obtain optimum properties. Subsequent processing includes a heat treatment step in order to provide a fine dispersion of said second additives uniformly precipitated throughout the matrix of the alloy. This fine dispersion is significant in obtaining desirable grain size, mechanical properties and especially stress and relaxation. The grain size of the alloys of the present invention is generally below 0.060 mm., and generally below 0.010 mm. if the alloys contain the first additive.

The alloy is then cold rolled at a temperature below 200C, with or without intermediate annealing. Annealing may be performed using strip or batch processing with holding times of from 10 seconds to 24 hours atfrom 250C to 850C. The final condition of the material may be either temper rolled strip or heat treated strip, depending upon desired properties. Naturally, a plurality of cold rolling and annealing cycles may be employed.

If the alloy of the present invention contains the second additive referred to hereinabove, the interannealing steps should be strip annealing and should include rapid cooling following annealing so that said second additive may be retained in solution as long as desired. When the alloy processed herein contains said second additive, the processing cycle. must include an annealing step at a temperature of from 250 to 600C for from 15 minutes to 24 hours in order to bring said second additive out of solution to provide the fine, uniform precipitation of said second additive dispersed throughout the alloy matrix. Naturally, this annealing step may be performed in the cold rolling annealing sequence, or as a final heat treatment in the processing cycle. If the annealing step to precipitate the second additive is performed as part of the cold rolling annealing sequence, any subsequent anneals must be batch type anneals at or below the temperature of the precipitation, i.e., from 25 to 600C for from 15 minutes to 24 hours and at no higher a temperature than the precipitation temperature that is employed. Naturally, the annealing steps prior to the precipitation annealing step may be as indicated above for from seconds to 24 hours at from 250 to 850C.

The processing cycle should contain a heat treatment step either as an interanneal or final anneal whether or not the second additive is present in the particular alloy. This heat treatment step during the processing cycle is necessary in order to obtain improvement in the strength of ductility relationship with or without the additives preferred herein. As indicated hereinabove, this heat treatment step is at a temperature range of from 250 to 850C for at least 10 seconds.

In accordance with the process of the present invention, the resultant material may then be formed into any desired part, such as a spring. One might prefer to perform a heat treatment step on the formed part in order to provide greater stress relaxation properties. This heat treatment step should be conducted at a temperature of from 150 to 400C for from minutes to 8 hours.

In the foregoing specification all percentages of ingredients are weight percentages.

The process of the present invention will be more readily apparent from a consideration of the following illustrative examples.

EXAMPLE 1 Alloy A of the present invention, consisting of 3% silicon, 2.5% tin, 1.5% iron and the balance copper, was

cast from 1200C into a steel mold with a water-cooled copper base. The 10 lb. ingot was soaked at 750C for 2 hours and immediately hot rolled to 0.375 inch at a hot rolling finishing temperature in excess of 400C, followed by cold rolling to 0.100 inch at a temperature below 200C. The alloy was then annealed for 1 hour at 450C followed by further processing as follows to provide metal at 0.020 inch gage in the as-quenched and 40, 60 and cold rolled condition. Some metal was cold rolled directly to 0.020 inch gage, i.e., 80% cold rolled metal. Some metal was cold rolled to 0.050 inch gage, annealed at 450C for 1 hour and cold rolled to 0.020 inch gage, i.e., 60% cold rolled metal. Some metal was cold rolled to 0.033 inch gage, annealed at 450C for 1 hour and cold rolled to 0.020 inch gage, i.e., 40% cold rolled metal. Some of the 40% cold rolled metal was annealed at 0.020 inch gage at 450C for 1 hour to provide annealed metal, i.e., 0% reduction. The tensile properties of these conditions are listed in Table I below. These properties are compared with those of the commercial high strength copper base alloys, Alloy B (a commercial alloy designated as CDA Alloy 510 having the composition 4.4% tin, 0.07% phosphorus, and the balance essentially copper) and Alloy C (a commercial alloy designated as CDA Alloy 638 having the composition 2.7% aluminum, 1.7% silicon, 0.4% cobalt, balance essentially copper).

The data in Table I below clearly demonstrates the significantrolled temper strength advantages obtained in accordance with the present invention. In addition, the grain sizes of these alloys were as follows: Alloy A 0.005 mm; Alloy B 0.010 mm.; and Alloy C 0.005 mm. Both Alloy A of the present invention and commercial Alloy 638 were characterized by particulate phases uniformly distributed throughout the matrix. The particulate phase in the alloy of the present invention was a mixture of alpha iron and iron silicide.

Alloys A and C, processed as in Example I, in the 0% cold rolled, 40% cold rolled, 60% cold rolled and 80% cold rolled conditions, were subjected to stabilization (stress relief) anneals at about 320C for 1 hour. The bend properties for these stabilized materials were then measured. The resulting data presented in Table II below were based on plots of 0.2% offset yield strength versus the ratio of bend radius to thickness (R/t) so that the bend properties could be easily compared at an equivalent 0.2% yield strength. For comparison purposes the bend data was determined from published data for Alloy B and CDA Alloy 688 (Alloy D having the composition 22.7% zinc, 3.5% aluminum, 0.38% cobalt, balance essentially copper) and is included in Table II.

The bend properties determine the minimum radius about which strip could be bent without cracking either parallel to or perpendicular'to the rolling direction. The longitudinal properties refer to the axis perpendicular to the rolling direction (goodway) and the transverse properties refer to the axis parallel to the rolling direction (badway); R is the smallest radius which does not crack and't is the thickness of the strip, i.e., all at 0.020 inch gage. It is significant that the present invention offers better goodway bend properties than commerical CDA Alloys 638 and 688 and better badway bend properties than commercial CDA Alloys 510 and 638. It is particularly significant that the alloy of the stress corrosion parameter of most interest is the time for 80% springback. The higher the value of this parameter, the more resistant the alloy to stress corrosion in the particular environment. The stress corrosion data and the transverse tensile properties are shown in Table III below. For comparison, similar data are shown for commercial CDA Alloy 510 (Alloy B) and commercial CDA Alloy 638 (Alloy C). These data clearly show the excellent stress corrosion resistance obtained in accordance with the present invention. It can be clearly seen that tin alone, as in commerical CDA Alloy 510, does not provide the desired resistance to stress corrosion. Furthermore, silicon in combination with another element such as aluminum, does not yield the excellent resistance to stress corrosion as does the present invention. Therefore, it is most surprising that the silicon and tin combination in accordance with the present invention provides such excellent stress corrosion resistance.

TABLE III STRESS CORROSION RESISTANCE Time for 80% Springback in Transverse Mech Properties Moist Ammonia Alloy 0.2% YS, ksi UTS, ksi Elongation, Hours Cu-3.5Si-I.8Sn0.0lFe I02 I33 3.0 I008 Cu-2.5Si-3.0Sn-0.01Fe I07 I34 4.7 1008 CDA 510 93 106 4.0 205 CDA 638 I01 I26 5.5 27.5

Tested at 0.030" gage in the 50% cold rolled condition. 7

present invention has adequate ductility at strength lev- EXAMPLE Iv els the other alloys cannot obtain.

EXAMPLE III Copper base alloys of the present invention containing silicon, tin and iron were chill cast as lb. ingots as in Example I. They were processed as in Example I and annealed to provide metal at 0.030 inch gage in the 50% cold rolled temper as follows: hot roll from 750C to 0.375 inch gage with a finishing temperature above 400C; cold roll below 200C to 0.120 inch gage; anneal at 450C for I hour; cold roll to 0.060 inch gage below 200C; anneal at 450C for 1 hour; and cold roll 50% to 0.030 inch gage at below 200C. The alloys were stress corrosion tested in moist ammonia in the following manner. The amount of springback after removal from a test jig was measured versus exposure time with U-bend shaped specimens. In this test the In this example additionaldata was obtained showing properties for a variety of materials. Alloy A, B, C, and D are as indicated hereinabove. Alloys E, F, G, H, and I have the compositionset forth in Table IV-A below. Alloys A and E through I were processed in a manner after Examples I and II as set out below: hot roll from 750C to 0.375 inch gage with a finishing temperature above 400C; cold roll to 0.l20 inch gage at below 200C; anneal at 450C for I hour; cold roll 67% to 0.040 inch gage at below 200C; anneal at 450C for l houryand cold roll 50% to 0.020 inch gage at below 200C. The resultant tensile and bend properties are shown in Table lV-B and Table IV-C below. For comparison purposes similar data is shown for Alloys B, C and D.

TABLE IV-A COMPOSITION Alloy Silicon Tin 70 Cobalt Iron 7:

E 3.0 2.5 1.5 F 1.5 4 G 2.0 4 H 2.0 3.5

TABLE IV-B TENSILE PROPERTIES TABLE'lV-B TENSlLE PROPERTlES-continued A i Ultimate I 0.2% Yield Tensile Cold Strength Strength Elongation Alloy Reduction (ksi) (ksi) TABLE lv-C BEND PROPERTIES 02% Yield Strength Longitudinal Transverse Alloy (ksi) /t R/t A 100 1.3 3.8 B 100 1.0 5.2 C 100 1.9 5.2 D 100 2.2 2.1 E 100 1.2 4.6 F 100 1.2 5.0 G 100 1.6 4.7 H 100 0.8 3.8 l 100 1.2 3.0

The foregoing data clearly shows that the alloys of the present invention have higher yield strength than Alloys B and C for equivalent cold reduction. Specifically referring to Table lV-C, the bend data shows that the alloys of the present invention have better longitudinal (goodway) bend properties at comparable yield strength than the comparative alloys excluding Alloy B, and have better transverse (badway) bend properties than the comparative alloys excluding Alloy D.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by'the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein."

What is claimed is:' i

l. A process which comprisesi A. providing a copper base alloy consisting essentially of from 1.0 to 4.5% silicon, from 1.0 to 510% tin, balance copper, wherein the total silicon plus "tin'content is at least 3.5%; l B. hot rolling said alloy at a starting temperature in excess of 650C and within 50C of the solidus temgroup vconsisting of from 0.01 to 2.0% iron, from 0.01

to 2.0% cobalt and mixtures thereof, with a maximum total iron plus cobalt being 3.0%.

3. A process according to claim 2 wherein said copper base alloycontains a second additive selected from the following group and mixtures thereof: Nickel from 0.01 to 5.0%,,manganese from 0.01 to 5.0%, titanium from 0.01 to 5.0%, zirconium from 0.01 to 5.0%, hafnium from 0.01 to 5.0%, chromium from 0.01 to 2.0%, beryllium. from 0.01 to 3.0%, vanadium from 0.01 to 5.0%, and magnesium from 0.01 to 2.0%, wherein the total content of said first additive plus said second additive is less than 10.0%.

4. A process according to claim 3 wherein said copper base alloy contains a third additive selected from the following group and mixtures thereof: from 0.01 to 3.0% each of arsenic, antimony, aluminum and zinc, wherein the total of said third additive is less than 5.0%.

5. A process according to claim 3 wherein prior to hot rolling the alloy is heated at temperature between 600C and the solidus temperature for at least 15 minutes.

6. A process according to claim 3 wherein the alloy is quenched to room temperature following hot rolling in order to maximize the amount of additives which remain in solution.

7. A process according to claim 3 wherein said cold rolling and annealing steps are repeated at least once.

8. A process according to claim 3 including a final heat treatment step inv the temperature range of from 250 to 600C for from 15 minutes to 8hours in order to provide a fine uniform precipitation of said second additive dispersed throughout the alloy matrix.

9. A process according to claim 3 wherein the resultant product is temper rolled strip.

10. A process according to claim 3 wherein the resultant product is formed into a part and said part is heat treated at a temperature of from to 400C for from 15 minutes to 8 hours. 

1. A PROCESS WHICH COMPRISES: A. PROVIDING A COPPER BASE ALLOY CONSISTING ESSENTIALLY OF FROM 1.0 TO 4.5% SILICON, FROM 1.0 TO 5.0% TIN, BALANCE COPPER, WHEREIN THE TOTAL SILICON PLUS TIN CONTENT IS AT LEAST 3.5%; B. HOT ROLLING SAID ALLOY AT A STARTING TEMPERATURE IN EXCESS OF 650*C AND WITHIN 50*C OF THE SOLIDUS TEMPERATURE OF THE ALLOY, AND WITH A FINISHING TEMPERATURE IN EXCESS OF 400*C; C. COLD ROLLING THE ALLOY AT A TEMPERATURE BELOW 200*C; AND D. ANNEALING THE ALLOY AT A TEMPERATURE OF FROM 250* TO 850*C FOR FROM 10 SECONDS TO 24 HOURS.
 2. A process according to claim 1 wherein said copper base alloy contains a first additive selected from the group consisting of from 0.01 to 2.0% iron, from 0.01 to 2.0% cobalt and mixtures thereof, with a maximum total iron plus cobalt being 3.0%.
 3. A process according to claim 2 wherein said copper base alloy contains a second additive selected from the following group and mixtures thereof: Nickel from 0.01 to 5.0%, manganese from 0.01 to 5.0%, titanium from 0.01 to 5.0%, zirconium from 0.01 to 5.0%, hafnium from 0.01 to 5.0%, chromium from 0.01 to 2.0%, beryllium from 0.01 to 3.0%, vanadium from 0.01 to 5.0%, and magnesium from 0.01 to 2.0%, wherein the total content of said first additive plus said second additive is less than 10.0%.
 4. A process according to claim 3 wherein said copper base alloy contains a third additive selected from the following group and miXtures thereof: from 0.01 to 3.0% each of arsenic, antimony, aluminum and zinc, wherein the total of said third additive is less than 5.0%.
 5. A process according to claim 3 wherein prior to hot rolling the alloy is heated at temperature between 600*C and the solidus temperature for at least 15 minutes.
 6. A process according to claim 3 wherein the alloy is quenched to room temperature following hot rolling in order to maximize the amount of additives which remain in solution.
 7. A process according to claim 3 wherein said cold rolling and annealing steps are repeated at least once.
 8. A process according to claim 3 including a final heat treatment step in the temperature range of from 250* to 600*C for from 15 minutes to 8 hours in order to provide a fine uniform precipitation of said second additive dispersed throughout the alloy matrix.
 9. A process according to claim 3 wherein the resultant product is temper rolled strip.
 10. A process according to claim 3 wherein the resultant product is formed into a part and said part is heat treated at a temperature of from 150* to 400*C for from 15 minutes to 8 hours. 